Norway

Norway

Hywind and Sway - Norway's two floating turbine designs

23 November 2011
by Erin Gill

NORWAY: A few years ago the idea of building offshore wind farms just a few kilometres from land seemed a technical challenge too far. Now, with an increasing number of countries working towards exploiting their offshore wind resources in relatively shallow waters, the next frontier is deeper waters.

The Hywind test turbine has been working at a high capacity

With fixed foundations struggling to cope in waters much deeper than 50 metres, the seemingly utopian dream of floating turbines installed in deep-water locations — able to harness power from the high winds that often feature further offshore — may become a reality before long.

One company doing much to push offshore floating wind technology toward commercialisation is Norwegian energy firm Statoil. Better known as an oil and gas company, Statoil has been investigating the technology for more than a decade. In September 2009 these efforts moved up a step, when the world’s first large-scale turbine floating in deep water began operating for a two-year trial.

Two years of data

The Hywind installation is located 12 kilometres off Norway’s south-west coast, in water approximately 220 metres deep. The floating aspect of the design is based around a 100-metre cylindrical steel substructure that descends vertically and can reportedly float in waters up to 700 metres deep. Designed by Finnish engineering firm Technip, the substructure is filled with water and rock ballast and anchored to the sea floor by three wires. Atop this substructure sits a Siemens SWT 2.3MW turbine.

Statoil’s enthusiasm for the potential offered by floating wind technology has grown as data from the Hywind trial has accumulated. In less than two years the turbine generated 15MWh of electricity.

"The capacity factor so far in 2011 is above 46%, and this is before the windy season starts," explains Dr Nenad Keseric, who is responsible for optimising Hywind’s electricity generation.

Keseric identifies several reasons for the success of the Hywind trial beyond the simple fact that a floating substructure has allowed the turbine to be installed in a previously inaccessible location which has high average wind speeds. A crucial advantage has been a comprehensive array of monitoring equipment that provides early warnings of possible failures.

This has allowed a regime of preventive maintenance, according to Statoil. In addition, an active motion controller was developed, which takes advantage of the turbine’s ability to dampen the wave-induced motions, and aids load reduction and performance of the turbine.

Support network

The Hywind trial has also benefited from Statoil’s policy of negotiating a hands-on approach with the companies that supplied key components. Instead of delivering the components and then leaving Statoil to face technical challenges on its own, the suppliers that came together to build the Hywind structure have remained involved, making their expertise available during the trial and delivering continuous operational improvements.

Given the success of this project, Statoil has been exploring how to take the next step towards commercialisation of floating offshore wind energy. Its home country of Norway does not have a strong appetite for such installations despite the fact that its government, through state-owned green-energy firm Enova, has financially supported Hywind and other Norwegian companies keen to develop offshore wind technology (see Thinking Big below).

Blessed with ample energy resources, including low-cost hydropower, Norway does not need wind power as urgently as other countries do. But, the Hywind turbine is not about to be dismantled and Statoil plans to continue to collect data throughout 2012.

Scottish potentialThe company has not had to look far afield to find political support for its future floating wind ambitions, with the Scottish government keen to provide a site for the next experiment. Plans for a wind farm with three to five floating turbines in Scottish waters have progressed sufficiently for an environmental impact assessment to have been commissioned this year.

Another location under consideration for a multi-turbine trial is off the Maine coast, in the north-east United States. Wherever the next trial — or trials — take place, Statoil is bullish about the future of floating offshore wind, stating that it is committed to further Hywind projects.

Statoil has so far invested around €50 million in floating wind-power technology and looks set to spend considerably more over the coming years. The company believes that one day the cost of generating electricity in difficult, high-wind yield, deep-water locations will be viable — and that it may not be too far off.

Despite the fact that floating wind farms operating high megawatt turbines in deep water have yet to be built, firm efforts are already under way to ensure that their eventual costs are minimised. Producing a competitively priced turbine is at the forefront of Ingelise Arntsen’s mind. Arntsen is chief executive of Sway Turbine, a Norwegian firm working on a 10MW turbine designed for both floating and fixed foundations.

"[Being] lightweight has been a main design criteria," explains Arntsen, acknowledging weight’s crucial importance in the total cost of a turbine. "The ability to scale up to larger turbine sizes without severe penalty on weight and costs will provide opportunities to reduce numerous other costs, such as number of installations, towers, foundations and number of turbines to be visited for operations and maintenance," she adds.

This year, Sway Turbine has been implementing its "technology qualification plan" and will finalise engineering by year-end. The next step will be a full-scale prototype, which will have an upwind configuration and a fixed-bottom foundation. Why the latter? Although Sway Turbine has often attracted attention due to its links to companies at the forefront of floating turbine technology — Statoil is a shareholder and sister company Sway is testing its full-scale floating tower — its turbine will be versatile and suitable for onshore, offshore fixed and offshore floating installations.

Floating versus fixed

While supplying floating installations remains on the agenda, Arntsen believes that fixed foundation offshore installations have a head start when it comes to bringing deep-water solutions to the market. "Based on current market signals, we believe fixed-foundation solutions will develop faster than deeper water floating solutions," she says. "Not necessarily because of cost, but due to perceived risk from investors. We think most investors initially will feel more comfortable with the application of more ‘known’ fixed foundation solutions."

However, Arntsen is excited about the prospect of more rapid deployment of floating wind technologies in Japan. In September, Japan’s trade ministry announced a ¥10-20 billion ($130-260 million) project to install a 1GW floating wind development in deep waters off its northern coast by 2020.

Japan’s decision to accelerate deployment of floating offshore wind is part of an apparent shift towards renewables in the aftermath of the earthquake and tsunami that hit the country in March.

In sharp contrast to the damage done to the country’s nuclear power stations, and the lasting human health fears this has raised, the Kamisu near-shore wind farm on Japan’s east coast withstood the extreme weather conditions and contributed much-needed electricity in the disaster’s immediate aftermath.

Leaving the shallow waters behind

A few years ago the idea of building offshore wind farms just a few kilometres from land seemed a technical challenge too far. Now, with an increasing number of countries working towards exploiting their offshore wind resources in relatively shallow waters, the next frontier is deeper waters.

With fixed foundations struggling to cope in waters much deeper than 50 metres, the seemingly utopian dream of floating turbines installed in deep-water locations — able to harness power from the high winds that often feature further offshore — may become a reality before long.

One company doing much to push offshore floating wind technology toward commercialisation is Norwegian energy firm Statoil. Better known as an oil and gas company, Statoil has been investigating the technology for more than a decade. In September 2009 these efforts moved up a step, when the world’s first large-scale turbine floating in deep water began operating for a two-year trial.

Two years of data

The Hywind installation is located 12 kilometres off Norway’s south-west coast, in water approximately 220 metres deep. The floating aspect of the design is based around a 100-metre cylindrical steel substructure that descends vertically and can reportedly float in waters up to 700 metres deep. Designed by Finnish engineering firm Technip, the substructure is filled with water and rock ballast and anchored to the sea floor by three wires. Atop this substructure sits a Siemens SWT 2.3MW turbine.

Statoil’s enthusiasm for the potential offered by floating wind technology has grown as data from the Hywind trial has accumulated. In less than two years the turbine generated 15MWh of electricity.

"The capacity factor so far in 2011 is above 46%, and this is before the windy season starts," explains Dr Nenad Keseric, who is responsible for optimising Hywind’s electricity generation.

Keseric identifies several reasons for the success of the Hywind trial beyond the simple fact that a floating substructure has allowed the turbine to be installed in a previously inaccessible location which has high average wind speeds. A crucial advantage has been a comprehensive array of monitoring equipment that provides early warnings of possible failures.

This has allowed a regime of preventive maintenance, according to Statoil. In addition, an active motion controller was developed, which takes advantage of the turbine’s ability to dampen the wave-induced motions, and aids load reduction and performance of the turbine.

Support network

The Hywind trial has also benefited from Statoil’s policy of negotiating a hands-on approach with the companies that supplied key components. Instead of delivering the components and then leaving Statoil to face technical challenges on its own, the suppliers that came together to build the Hywind structure have remained involved, making their expertise available during the trial and delivering continuous operational improvements.

Given the success of this project, Statoil has been exploring how to take the next step towards commercialisation of floating offshore wind energy. Its home country of Norway does not have a strong appetite for such installations despite the fact that its government, through state-owned green-energy firm Enova, has financially supported Hywind and other Norwegian companies keen to develop offshore wind technology (see Thinking Big below).Blessed with ample energy resources, including low-cost hydropower, Norway does not need wind power as urgently as other countries do. But, the Hywind turbine is not about to be dismantled and Statoil plans to continue to collect data throughout 2012.

Scottish potentialThe company has not had to look far afield to find political support for its future floating wind ambitions, with the Scottish government keen to provide a site for the next experiment. Plans for a wind farm with three to five floating turbines in Scottish waters have progressed sufficiently for an environmental impact assessment to have been commissioned this year.

Another location under consideration for a multi-turbine trial is off the Maine coast, in the north-east United States. Wherever the next trial — or trials — take place, Statoil is bullish about the future of floating offshore wind, stating that it is committed to further Hywind projects.

Statoil has so far invested around €50 million in floating wind-power technology and looks set to spend considerably more over the coming years. The company believes that one day the cost of generating electricity in difficult, high-wind yield, deep-water locations will be viable — and that it may not be too far off.

Despite the fact that floating wind farms operating high megawatt turbines in deep water have yet to be built, firm efforts are already under way to ensure that their eventual costs are minimised. Producing a competitively priced turbine is at the forefront of Ingelise Arntsen’s mind. Arntsen is chief executive of Sway Turbine, a Norwegian firm working on a 10MW turbine designed for both floating and fixed foundations.

"[Being] lightweight has been a main design criteria," explains Arntsen, acknowledging weight’s crucial importance in the total cost of a turbine. "The ability to scale up to larger turbine sizes without severe penalty on weight and costs will provide opportunities to reduce numerous other costs, such as number of installations, towers, foundations and number of turbines to be visited for operations and maintenance," she adds.

This year, Sway Turbine has been implementing its "technology qualification plan" and will finalise engineering by year-end. The next step will be a full-scale prototype, which will have an upwind configuration and a fixed-bottom foundation.

Why the latter? Although Sway Turbine has often attracted attention due to its links to companies at the forefront of floating turbine technology — Statoil is a shareholder and sister company Sway is testing its full-scale floating tower — its turbine will be versatile and suitable for onshore, offshore fixed and offshore floating installations.

Floating versus fixed

While supplying floating installations remains on the agenda, Arntsen believes that fixed foundation offshore installations have a head start when it comes to bringing deep-water solutions to the market. "Based on current market signals, we believe fixed-foundation solutions will develop faster than deeper water floating solutions," she says. "Not necessarily because of cost, but due to perceived risk from investors. We think most investors initially will feel more comfortable with the application of more ‘known’ fixed foundation solutions."

However, Arntsen is excited about the prospect of more rapid deployment of floating wind technologies in Japan. In September, Japan’s trade ministry announced a ¥10-20 billion ($130-260 million) project to install a 1GW floating wind development in deep waters off its northern coast by 2020.

Japan’s decision to accelerate deployment of floating offshore wind is part of an apparent shift towards renewables in the aftermath of the earthquake and tsunami that hit the country in March.

In sharp contrast to the damage done to the country’s nuclear power stations, and the lasting human health fears this has raised, the Kamisu near-shore wind farm on Japan’s east coast withstood the extreme weather conditions and contributed much-needed electricity in the disaster’s immediate aftermath.